As an oncogenic factor, miR‐222 was found to inhibit the expression of tricho‐rhino‐phalangeal syndrome type 1 protein (TRPS1) and promote the process of epithelial‐to‐mesenchymal transition (EMT), leading to acquisition of chemo‐resistance and formation of aggressive phenotype of breast cancer.30 Another study showed that miR‐222 was highly enriched in the exosomes secreted by chemo‐resistant breast cancer cells (MCF‐7/Adr and MCF‐7/Doc). This evidence concerns the gene TRPS1 and breast cancer.